The invention relates to an electric circuit assembly comprising a network of printed circuit conductors on a printed wiring board and a number of circuit components which are interconnected through the conductors.
It is known to provide printed circuits or conductors on printed circuit boards, to insert circuit components into holes in the boards, and to connect the various parts of the circuit at the connection places, for example by soldering, in particular by immersing in a solder bath. The material of the printed circuit boards is usually a glass fibre-reinforced polyester resin which satisfies the imposed requirements as regards thickness and rigidity.
It has been found that the properties of the electric circuits built up in the above-described manner can vary when the moisture content of the ambient air varies. This relates in particular to variations in the oscillator frequency of oscillator circuits; for example, those present in U.H.F. tuners. The most critical point proves to be the top of the oscillator resonant circuit. It has been found that the stray capacitance of the printed circuit board at this point varies under the influence of moisture and causes variations in the oscillator frequency.
The invention provides a particularly simple and effective solution to reduce this problem.